In a radio-frequency (RF) accelerating cavity used for a charged particle accelerator, RF electrical power is accumulated in a metal housing, and charged particles such as electrons and ions are artificially accelerated to high speed by using RF electric field generated in the housing. Accelerators using a RF accelerating cavity are widely used in, for example, the academic fields of high-energy physics experiments and synchrotron radiation facilities and the industrial fields of radiation therapy and diagnostic devices and sterilization devices.
Typically, a RF accelerating cavity is roughly classified into a normal-conducting accelerating cavity that is made of high-purity copper and operates at room temperature, and a superconducting accelerating cavity that is made of superconductive material (for example, niobium) and operates at extremely low temperature.
PTL 1 discloses an invention related to an accelerating structure produced by alternately joining a ring-shaped acceleration member made of non-magnetic refractory metal and a ring-shaped electrical insulation member made of ceramic. PTL 2 discloses an invention related to an accelerating cavity produced by alternately connecting a basic cavity and a disk in an acceleration direction, in which the basic cavity and the disk are manufactured by forming two layers of an active silver brazing filler metal layer and a copper electroforming layer on the surface of each of a ceramic cavity and a ceramic circular disk.